1. Field of the Invention
The present invention relates to a display control apparatus and a display control method, which play back contents drawn in a drawing area for drawing an object.
2. Description of the Related Art
Recently, large screen display apparatuses represented by a plasma display and also including a rear-projection display and a front projector have been widespread. Presentations, conferences, and school lessons using such a large screen display apparatus are becoming popular.
In a conference or school lesson using a large screen display apparatus, a user conventionally uses a pointing rod or a laser pointer as a means for indicating a specific position on the display screen.
However, a pointing system having a digitizer for detecting a position (indicated position) on the display screen indicated by a user is developed recently and used often. This pointing system can move a cursor on the display screen in correspondence with a position indicated by a user, or generate a drawn object such as a character or graphic pattern on the display screen by activating a tool corresponding to an indicated position. The system can also freely edit the generated drawn object.
Such a pointing system generally connects a large screen display apparatus to the video output terminal of a display control apparatus such as a personal computer, thereby displaying display data generated by the personal computer on the large screen display apparatus. The system also connects the digitizer to the personal computer using an interface cable and transmits information about an indicated position via the interface cable.
Additionally, an application for reflecting information about an indicated position input via the interface cable on cursor movement or generation of a drawn object such as a character or graphic pattern is installed on the personal computer side.
The pointing system having the above-described arrangement can implement various functions by expanding the functions of the installed application.
For example, direct drawing corresponding to an indicated position on the display screen implements a handwriting input function. This makes the large screen display apparatus usable as an electronic whiteboard.
When drawn contents displayed on the display screen change in accordance with a user operation, the contents of the change are recorded together with time data and played back along the time data. This system arrangement implements a playback function. This playback function allows playing back drawn contents displayed on the display screen during a conference along with the elapse of the time of conference. Hence, if, for example, the large screen display apparatus is used as an electronic whiteboard, the playback contents can be used as a conference report.
Various proposals have been made for the playback function of playing back change contents recorded together with time data.
For example, Japanese Patent Laid-Open No. 2004-336289 discloses a snapshot of a whiteboard as a target to be recorded for the purpose of playback by the playback function. This enables playback of a conference or school lesson. Japanese Patent Laid-Open No. 6-205151 discloses an arrangement for playing back voice/image information during a conference, too.
A proposal for improving user convenience in playback using the playback function has also been made. For example, to shorten the playback time, not only the normal-rate playback mode but also functions such as a fast-forward mode and a double-rate playback mode have been proposed.
Japanese Patent Laid-Open No. 11-112922 discloses an arrangement for analyzing an event point such as an image change point or voice speaker change point from input image or voice stream data. According to this prior art, when an event point is detected during playback, the stream near the event point is played back slowly, thereby allowing a user to easily recognize a specific stream.
However, there are several problems in applying the playback function aiming at improving user convenience to the pointing system. For example, the playback function plays back even a drawn object that a user temporarily input by handwriting and immediately erased, that is, a drawn object that is not directly relevant to grasp of, for example, conference contents. If a user inputs the strokes of characters one by one by handwriting, the strokes of each drawn object input by handwriting are sequentially played back one by one, resulting in long playback time.
The playback time is short in playback using the fast-forward mode or double-rate playback mode. However, a portion necessary for grasping the playback contents is also played back at a high speed. This impedes the user from grasping the playback contents.
There is also an arrangement for analyzing each recorded drawn object and detecting an event point, thereby slowly playing back data near the event point, as in Japanese Patent Laid-Open No. 11-112922. However, this method requires analysis of a recorded drawn object, resulting in complex processing.